Method of producing low oxygen oriented silicon-iron



Feb. 21, R? R. E. BONI ETAL METHOD OF PRODUCING LOW OXYGEN ORIENTED SILICON-IRON Filed Dec; 17, 1964 omn oom

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Wdd .LNlLNOO NEISAXO United States Patent 3,305,354 METHOD OF PRODUCING LOW OXYGEN ORIENTED SILICON-IRON Robert E. Boni, Middletown, and Joseph E. Heck, Monroe, Ohio, assignors to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Filed Dec. 17, 1964, Ser. No. 419,023 8 Claims. (Cl. 75-129) In the manufacture of silicon-iron for magnetic purposes, particularly where the ultimate sheet stock has a preferred orientation, the economic provision of an iron material having initially a low oxygen content or a low content of oxide inclusions has been known to be of great advantage. By way of example, silicon-iron material which is intended for the manufacture of sheet stock having the so-called cube-on-face texture or orientation in which two cube faces or (100) planes are parallel to the sheet surface, should not have at the outset an oxygen content of more than about .0040%. Siliconiron sheet stocks having the so-called cube-on-edge orien tation have improved magnetic properties when made from materials of initially very low oxygen content. Also, although the oxygen may be removed from the solid material during an annealing treatment, this prior technique requires higher temperatures and longer times at temperature.

Hitherto, in the manufacture of silicon-irons of low oxygen values, the best procedures have involved vacuum melting or remelting in the consumable electrode furnace, both of which procedures are relatively expensive. It is an object of this invention to provide a method whereby silicon-irons of other origins can be made in such a way as to have very low oxygen contents at the outset. By the term other origins is meant the production of the iron in basic open hearth or electric furnaces, or by those methods in which the molten metal in a suitable container is blown with oxygen.

Silicon-iron is defined for purposes of this invention as being an alloy containing from about 2.5% to about 3.5% of silicon, enough manganese for workability, minor amounts of such elements as carbon, sulfur and phosphorus, the balance being iron with only such impurities as are incident to the mode of manufacture. It has hitherto been suggested that the alloying with the principal alloying elements, silicon and manganese, be accomplished after the metal has been tapped from the furnace in which it was made. While it does not constitute a departure from the spirit of the invention to accomplish part of the alloying in a furnace such as the open hearth and the remainder of the treatment in the ladle from which the molten metal will be teemed into the ingot molds, it is preferred to employ a re-ladling procedure in which part of the treatment is accomplished in a first ladle, after which the molten metal is poured into a second ladle and the remainder of the treatment accomplished therein or during the transfer of the metal from the first ladle to the second. However, it will be understoodthat wherever mention of additions to first and second ladles or first and second vessels is made in the present specification and claims, the first vessel may be the furnace.

Nevertheless, and particularly in the manufacture of silicon-iron sheet stock having cubic texture, i.e., the special type of cube-on-face orientation designated (100) 3,305,354 Patented Feb. 21, 1967 "ice [001] by Millers Indices, the most consistent results have been attained by (a) vacuum melting or remelting by the use of the consumable electrode furnace, or (b) manufacturing a sheet stock which has another orientation and has been subjected to a final high temperature heat treatment serving to diminish the quantity of oxide inclusions, and then converting such stock to the cubic texture by procedures known in the art.

It is an object of this invention to provide a method of making silicon-iron whichinitially has a very low oxygen content as teemed into the ingot molds, but without resorting to any of the expedients set forth in the preceding paragraph.

It is a further object of the invention to provide siliconiron in cast form which can, by known rolling and annealing steps, be made into either cube-on-edge or cubeon-face oriented sheet stock consistently, at lower cost, and with improved magnetic properties.

These and other objects of the invention which will be set forth hereinafter or Will be apparent to one skilled in the art upon reading these specifications, are accomplished by that procedure of which exemplary embodiments will now be described. Reference is made to the figure wherein oxygen content in parts per million is plotted against pounds of FeSi added to the first ladle.

In the standard procedure in the art it has been the practice to tap the molten metal from the furnace or vessel in which it has been refined into a first ladle and to add to it a relatively small amount of silicon-bearing material, together with manganese-bearing material. For example, the silicon can be added in the form of ferrosilicon, while the manganese can be added in the form of .silico-manganese, ferro-manganese, or electrolytic manganese. The term adding is used in the broad sense since the alloying elements may be mixed with the molten metal in the furnace, in the tap runner before the metal gets to the first ladle, or placed in the first ladle with the molten metal deposited on top of them. Also, the alloying elements may be fed into the first ladle concurrently with the introduction of the molten metal. The procedure is in any event rapid, and the partially treated metal will not stand longer than two or three minutes after alloying and before transference to the second ladle.

It has been the endeavor in the past to add enough manganese-bearing substance in the first ladle to bring the manganese up to the desired final level which is about .04% to about .12%. At the same time the quantity of silicon-bearing material added to the first ladle has been relatively small and not suflicient to kill the steel.

In the second ladle, that is to say in any of the ways set forth above, it has been the practice to add the remainder of the silicon-bearing material necessary to raise the silicon value of the alloy to the desired final level. Also, it has been the practice to add aluminum to the second ladle for its deoxidizing effect and for ease in pouring. But by the procedure outlined above it has not been possible consistently to produce an alloy containing less than about .010% oxygen.

By way of contrast the new procedure taught herein contemplates the addition of a very much larger part of the ferrosilicon to the first ladle, together with electrolytic manganese to attain the same final manganese content. Other forms of manganese-bearing materialmay be used if desired. In the second ladle the remainder of the silicon-bearing material is added together with somewhat less aluminum than was formerly used.

Surprisingly, the relatively simple change in procedure results in a marked difference in oxygen level in is preferably -very low in residual aluminum (less than 0.25%). If the aluminum content of the ferrosilicon is greater than 0.25%, the amount of aluminum added as shot or bar to the second ladle may be reduced proportionally below 60 lbs. for a 150 ton heat.

the molten metal. The process of this invention can be It is also preferable to make the additions to the stream depended upon to produce a silicon-iron containing about of molten metal as it flows between the vessels to obtain .0040% or less oxygen. better mixing. The aluminum may be added separately The contrast between the two procedures is graphically or at the same time as the ferrosilicon, the latter being shown in the following chart: the preferred practice.

As will be understood by one skilled in the art, the 01d Procedure New Procedure oxygen content at tap may vary considerably depending upon the refining practice used. In accordance with the Filst Ladle; First Lame; new procedure, the amount of ferrosilicon added to the 100 lbs. 65% ferrosilicon 2501,250lbs. 05% ferrosilicon first l dl can b dj ted within the range of 1 to 8 for cubeoncdge stock. 7504,2501- 65% [emsmcon 10 lbs. per ton of charge to match the tap oxygen. When for cube-on-face stock.

450-700 lbs. silicomanganese 100-575lbs.mangancse (preii IS known that the cast metal W1 u1t1mat.ely.be made emb1ye1ecn-01yfic) into a cube-on-face product, such as cubic texture, a

Holding time: None (i.e. no Holding time: None or prel i i f bo t 5 lb of 65% f rrosilicon per ton of unnecessary delay before erably 5 to minutes. 1 re-ladliug). charge 1s requlred. The use of more than 8/3 lbs. per Second Ladle: Second Ladle:

15,000 lbs. 65% ferrosilicon-.. Balance 01' the ferrosilicon ton 1S unnecessary to obtam the deslred low oxygen con required to reach deslii'ed tent si icon content (usua y less 80 lb 1 60 ib i lbw Examples S. 01 more 3. urnmum .c 0 S. 3. uminnm. Holding time: About 20 min". Holding time: About 20 min. The followmg table summanzes the Procedure and re Average oxygen about 0.01% Average oxygen about 002.5%. SlllliS Obtained from 8 exemplary heats Of about 150 tons each. The core loss values are not given because the While 51% hold(i1nghti1e after the addition of thle alloyipg inlgredientg heats were rolled t0 various final gauges. However, the 1s require eyon e ilne necessary to transfer t 10 meta to t 1e secon ladle, more consistent results are attained with the brief holding times core 10S ses were to be 9 than those Obtamed by indicated. conventlonal deoxldizmg practices.

Additions to Additions to Ladle Analysis 2nd Percent 01' Straightlst Ladle, Lbs. Holding 211d Ladle, Lbs. Holding Ladle, Percent Percent Area of Sheet Grain Per- Heat lime lst Time 2nd Oxygen in Stock Having meability Number Ladle, Min. Ladle, Min. Ingot (Dip Cubic Texat 11 10 65% Elec. 65% Al O Mn S Si 'lest) ture Grains Oersteds FeSi M11 FeSi 250 400 None 14, 000 80 20 .023 .000 .027 3.27 .0074 None 1,808 500 575 None 14,800 80 20 .020 .000 028 3.15 .0056 None 1,820 750 500 None 14,000 80 22 .028 .124 .028 3. 03 .0030 85-90 1,311 1,000 450 None 14,400 80 20 .023 .118 025 3.00 .0024 100 1,803 1,000 315 None 15,000 None 20 .027 .100 028 3. 21 .0092 None 1,791 1,100 200 None 15, 300 00 25 .023 .080 024 3.04 .0028 100 1,707 1,100 110 10 13,000 75 20 .023 .004 .021 2.75 .0018 100 1,831 1,100 150 10 13,700 75 20 .024 .049 .023 2. 03 .0018 100 1,828

1 Contained very high percentage of cubc-on-edge grains.

The figures above are based on heats of about 150 tons It will be apparent that the new practice of increasing each. The total amount of silicon or silicon-bearing mathe deoxidation by silicon in the first ladle lowers conter1al for heats directly compared was the same. Fersiderably the final oxygen content of the ingot or hot ros1l1con may be obtalned having various percentages of band. Yet, as noted by the results for Heat 3248, it has s1l1con. The above figures are for the 65% ferrosilicon, been found that aluminum must still be added to the secbut these figures can be directly converted for other per- 0nd ladle. This synergistic effect of the combination of centages of ferros1l1con and for other heat sizes. For silicon and aluminum has not been heretofore recognized. example, if 90% ferrosllicon were used, only 72% as The reasons for the unexpected and surprising results much would be added to each ladle. Also, if a 300 ton obtained by the practice of this invention are obscure. heat were be1ng made, all addition would be doubled. Without wishing to be bound by theory, it nevertheless Based on the weight of the metal treated expressed in appears that aluminum as a getter for oxygen at the low short tons (2000 lbs.), the new procedure uses at least oxygen levels involved here is not effective unless the 1.67 lbs. /ton of 65 ferros1l1con in the first ladle commolten metal has first been treated with a very substantial pared With about 0.67 lb./ton 1n the prior practice, or at quantity of silicon, and in particular with enough siliconleast 2 /2 t1mes as much ferros1licon per heat in the manbearing material to leave a substantial residual quantity ufacture of sheetstock capable of being made into cubeof silicon in alloyed condition in the ferrous metal. A on-edge texture s1l1con-1ron. For making a cube-on face laboratory study indicated that aluminum serves to intype product, the m1n1mum first ladle addition of ferrocrease the rate of deoxidation of silicon-iron. By the sheen 1s about 5 lbs/ton of metal, or about 7%. times same token, the process of this invention operates to give asmuch as that formerly used. The maximum ferroa lower final oxygen content with the use of less alumisilicon add1t1on necessary for reducing the oxygen content num. of the metal to less than 6 p.p.m. is about 8.33 lbs./ton The holding times as set forth for the new procedure of metal, or more than 12 times the amount previously have been found beneficial in permitting oxide inclusions addedsuch as silicates and aluminates and their combinations If the alummum is also expressed in lbs/ton, the addi- With other oxides to float upwardly to the top of the metal t1on formerly used was at least .53 lb./ ton compared with bath. The prior practice of re-ladling as soon as the first about .40 to .53 lb./ton 1n the present practice. ladle is full may not allow enough time for the effective The manganese add1t1on of about to 575 pounds of deoxidation and removal of the resulting inclusions. The electrolyt1c manganese for a heat of tons may be exkinetics of the deoxidation reactions and the removal of pressed as about 0.67 to 3.84 lbs./ton of metal. the inclusions by flotation have not been studied. If

The ferros111con used 1n the practice of this invention 7 these impurities are not removed in the furnace or first ladle, they will be carried into the teeming ladle and from there into the casting. If sufficient additional ferrosilicon is added to the melting furnace to lower the oxygen content of the melt to a level requiring only a single ladle, this ladle should be held for about 20 minutes before the metal is teemed into molds or poured into a continuous casting machine.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of producing low oxygen silicon-iron intended for the manufacture of oriented silicon-iron sheet stock, comprising the steps of adding to molten ferrous metal in a first vessel a quantity of silicon-bearing material sufficient to combine with oxygen in the ferrous metal and to leave a substantial residual quantity of silicon in alloyed condition in the ferrous metal, addin a quantity of manganesebearing material to said first vessel SLlfilClCIliI to bring the manganese content of said ferrous metal up to a desired final level, transferring said ferrous metal to a second vessel, adding a quantity of said silicon-bearing material sufiicient to bring the silicon content of said ferrous metal to a desired final alloy level, adding aluminum to said ferrous metal, and holding said ferrous metal in said second vessel for a holding period sufiicient to allow inclusions to float out of said ferrous metal.

2. The process claimed in cliam 1 wherein said ferrous metal is held in both vessels and the holding period for said first vessel is about 515 minutes and the holding period for said second vessel is about 20 minutes.

3. The process claimed in claim 1 wherein the ferrous I metal charge is subsequently made into 'a sheet product having a cube-on-edge orientation and wherein the siliconbearing material added to the first vessel is ferrosilicon added in a quantity equivalent to at least 1 /3 pounds of 65% ferrosilicon per ton of said metal charge.

4. The process claimed in claim 1 wherein the ferrous metal charge is subsequently made into a sheet product having a cube-on-face crystallographic orientation and wherein the equivalent of at least 5 pounds of 65% ferrosilic-on is added to the first vessel per ton of said metal charge.

5. The process claimed in claim 3 wherein the said manganese addition to said first vessel is equivalent to about /3 pound to 4 pounds of manganese per ton of metal charge.

6. The process claimed in claim 3 wherein said aluminum addition to said ferrous metal in said second vessel is equivalent to about pound to about /2 pound per ton of metal charge.

'7. The process claimed in claim 4 wherein the said manganese addition to said first vessel is equivalent to about /3 pound to 4 pounds of manganese per ton of metal charge.

8. The proces claimed in claim 4 wherein said aluminum addition to said ferrous metal in said second vessel is equivalent to about /5 to about /2 pound per ton of metal charge.

No references cited.

BENJAMIN HENKIN, Primary Examiner. 

1. A METHOD OF PRODUCING LOW OXYGEN SILICON-IRON INTENDED FOR THE MANUFACTURE OF ORIENTED SILICON-IRON SHEET STOCK, COMPRISING THE STEPS OF ADDING TO MOLTEN FERROUS METAL IN A FIRST VESSEL A QUANTITY OF SILICON-BEARING MATERIAL SUFFICIENT TO COMBINE WITH OXYGEN IN THE FERROUS METAL AND TO LEAVE A SUBSTANTIAL RESIDUAL QUANTITY OF SILICON IN ALLOYED CONDITION IN THE FERROUS METAL, ADDING A QUANTITY OF MANGANESE-BEARING MATERIAL TO SAID FIRST VESSEL SUFFICIENT TO BRING THE MANGANESE CONTENT OF SAID FERROUS METAL UP TO A DESIRED FINAL LEVEL, TRANSFERRING SAID FERROUS METAL TO A SECOND VESSEL, ADDING A QUANTITY OF SAID SILICON-BEARING MATERIAL SUFFICIENT TO BRING THE SILICON CONTENT OF SAID FERROUS METAL TO A DESIRED FINAL ALLOY LEVEL, ADDING ALUMINUM TO SAID FERROUS METAL, AND HOLDING SAID FERROUS METAL IN SAID SECOND VESSEL FOR A HOLDING PERIOD SUFFICIENT TO ALLOW INCLUSIONS TO FLOAT OUT OF SAID FERROUS METAL. 